Metals, and in particular iron, steel and other iron alloys of various compositions and grades, are typically prepared by tapping molten material from a continuous melting furnace into a holding ladle from which the molten material may be poured into a mold to form an ingot or other cast product. The melt typically contains impurities detrimental to, or out of specification with, the desired ingot or product. Various deoxidizing compounds may be introduced below the surface of the ladle melt, or into the melting furnace, to control graphite content and remove oxygen and unwanted substances from the melt prior to pouring. De-oxidation refers to the removal of oxides and oxygen from molten metal and involves adding materials with a high affinity for oxygen, the oxides of which are either gaseous or readily form slags. The de-oxidation and desulphurization of steel is usually performed by adding, silicon (Si), aluminum (Al) or manganese (Mn). Common deoxidizing inoculants for such purposes include: ferrosilicon, ferromanganese, and calcium silicide which are sometimes used in the production of carbon steels, stainless steels, and other ferrous alloys; manganese which is often used in steelmaking; silicon carbide and calcium carbide which are commonly used as ladle deoxidizers in steel production; aluminum dross which can be used to deoxidize slag in secondary steelmaking; calcium which can used as a deoxidizer, desulfurizer, or decarbonizer for ferrous and nonferrous alloys, and titanium which can be used as a deoxidizer for steels.
As reflected by U.S. Pat. No. 2,444,424 to Brown et al., it has been known since about 1945 that granular silicon carbide (SiC), also known as carborundum, may be introduced to the ladle during steel pouring to significantly improve the quality of steel alloys. Silicon carbide must be of sufficiently fine sized particles to be readily dispersed within the steel melt as it enters the ladle in order to completely decompose into silicon and carbon for the deoxidation reactions to occur homogenously. The silicon carbide must be fed into the ladle as steel is entering the ladle at a controlled rate to assure complete sub-surface mixing of the reactants. Silicon carbide (SiC) offers substantial deoxidizing capabilities and exothermic benefits (i.e. thermal gain) to facilitate the controlled de-oxidizing process in steel manufacturing. In such processes, silicon carbide (SiC) decomposes at ladle temperatures in an exothermic reaction, which in addition to yielding substantial amounts of heat also yields silicon (Si) which acts as a reducing agent to strip oxides and carbon from the melt. The stripped carbon readily combines with oxygen to form carbon monoxide (CO) and/or carbon dioxide (CO2) which may escape from the melt as a gas or enhance the formation of graphite beneficial to various grades of steel. Silicon in the form of silicon carbide (SiC) has been demonstrated to provide benefits to high quality steel production which exceed those achievable by the use of elemental silicon (Si) or aluminum (Al). Brown et al. '424 teaches that the addition of silicon carbide in amounts ranging from as low as one point one pounds (1.1 lb.) to about eight pounds (8 lb.) of silicon carbide (SiC) per ton of molten steel provides marked improvements in the physical properties of the resulting steel. According to Brown et al. '424, use of about six (6) pounds of silicon carbide (SiC) per ton of steel is preferred for steels containing under zero point two percent by weight (0.2 wt %) carbon, use of about four (4) pounds of silicon carbide (SiC) per ton of steel is preferred for steels containing from zero point two percent by weight (0.2 wt %) to zero point four percent by weight (0.4 wt %) carbon, and use of about two (2) pounds of silicon carbide (SiC) per ton of steel is preferred for steels containing more than zero point four percent by weight (0.4 wt %) carbon.
Various industrial processes employ silicon carbide as an abrasive for cutting and/or surface finishing of steel, silicon, and various alloys. Examples of such processes include, but are not limited to: attrition grinding of steel bearings, vibratory finishing, polishing or de-burring of metallic parts. Silicon carbide is also included, together with silicon in either crystalline and/or polycrystalline form, in the waste material produced from wire saw slicing and squaring of photo-voltaic grade silicon, slicing, polishing of electronic grade silicon, and the like. These operations produce waste which typically includes fine particles of silicon carbide (SiC), metal alloys, silicon and carrying fluids such as glycol-based organic fluids. Vibratory finishing and polishing operation may also yield silicon carbide (SiC) and metal residue for recovery. The spent silicon carbide and abraded metal cuttings may be flushed to a recovery system for partial recycling and disposal as waste.
The demand for alternative sources of energy has spurred the production and commercialization of photovoltaic arrays for generating electricity from sunlight. Such arrays commonly include wafers of silicon, in either single crystalline form and/or polycrystalline form, the latter commonly referred to as “polysilicon”. Such wafers are produced at high cost and through the investment of substantial amounts of thermal energy. However, the useful life of photovoltaic arrays is limited and at the end of their useful life such arrays are typically scrapped and disposed of as waste.